The present invention relates in general to a process for reactive ion etching (RIE) of conductive layers used in semiconductor integrated circuits (IC). In particular, the invention relates to methods for RIE mode plasma etching of silicides, polycrystalline silicone (polysilicon) and composite silicide-on-polysilicon structures (polycide), to the use of the silicide layer as an etch mask during etching of the polysilicon and to a reactive gas composition for use in such methods.